Zero-magnetic-field dynamic scaling in Bi_2Sr_2CaCu_2O_8 thin films

Abstract

We investigate the zero-magnetic-field dynamic scaling in Bi_2Sr_2CaCu_2O_8 thin films from nonlinear current-voltage (I-V) characteristics and by using the concavity criterion recently proposed by Strachan [Phys. Rev. Lett. 87, 067007 (2001)] . We find that fresh samples show a BKT-like transition with z=0.8, smaller than expected for a conventional Berezinskii-Kosterlitz- Thouless transition. The effect of sample size and finite Josephson coupling are discussed. We examine the effect of thermally-induced disorder in the oxygen sublattice finding that the BKT-like transition is suppressed by point disorder.